linux-kernel - Re: [PATCH v2] x86: Early-boot serial I/O support

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Message-ID: <4C38E7FD.9020403@zytor.com>
Date:	Sat, 10 Jul 2010 14:37:01 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
CC:	Pekka Enberg <penberg@...helsinki.fi>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH v2] x86: Early-boot serial I/O support

On 07/10/2010 02:07 PM, Cyrill Gorcunov wrote:
> On Sat, Jul 10, 2010 at 10:40:20PM +0300, Pekka Enberg wrote:
>> This patch adds serial I/O support to very early boot printf(). It's useful for
>> debugging boot code when running Linux under KVM, for example. The actual code
>>  
>> +#define cpu_relax()	asm volatile("rep; nop" ::: "memory")
>> +

We don't need "memory" here since the early boot environment is
single-threaded.

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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